One of the most eagerly awaited medical experiments has begun in Nashville. For the first time, scientists have used the gene-editing technique called CRISPR to try to treat a genetic disorder in the United States. NPR is the only news organization to have learned the identity of the first patient and to talk with her. NPR health correspondent Rob Stein is here with more.

Hey, Rob.

ROB STEIN, BYLINE: Hey, Ari.

SHAPIRO: Who is this woman, and why is she undergoing this experimental treatment?

STEIN: Her name is Victoria Gray, and she's 34 and lives in Forest, Miss., with her husband and four kids. And here's a little bit about what she told me about herself when I met with her recently at the Sarah Cannon Research Institute in Nashville.

VICTORIA GRAY: Well, I don't work. I'm a stay-at-home mom. But before I got too sick, I was working in the beauty department at Walgreens, and I was going to school to become a nurse. But that got put on hold for health reasons.

SHAPIRO: Tell us about her sickness. What is her condition?

STEIN: Yeah, so Victoria has sickle cell disease, and it's a terrible genetic disease that primarily affects African Americans in the United States. And instead of having normal red blood cells - you know, the cells that carry oxygen in your body - sickle cell patients have a hard, sticky - it's a sickle-shaped red blood cell that causes terrible bouts of agonizing pain and can cause lots of really serious health problems.

GRAY: Well, I'm high-risk for strokes, and I'm high-risk for heart attacks. And these things can happen to me in a blink of an eye. And my pain episodes can just come on out of the blue. I can just be laughing, and next minute, I'm crying, you know, in some of the worst pain that you could ever imagine. It's a heavy load to carry, you know?

SHAPIRO: That sounds really tough. So how are doctors trying to use CRISPR to help people like Victoria Gray?

STEIN: Right, so this is how it works. The doctors - they take cells out of the bone marrow of sickle cell patients, and they use this CRISPR editing tool to edit a gene in those cells to turn on the production of something called fetal hemoglobin, which is usually only produced by fetuses when they're in the womb and babies for a short time after they're born. And then they infuse billions of these genetically modified cells from the patient back into their bodies, hopefully, to help treat their disease.

Dr. Haydar Frangoul, who's running the study in Nashville - he explained a little bit more about how this is going to work.

HAYDAR FRANGOUL: What we are trying to do here is we are trying to introduce enough fetal hemoglobin into the red blood cell to make the red blood cell go back to being happy, squishy and not sticky and hard and can go deliver oxygen where it's supposed to.

SHAPIRO: So she is the first sickle cell patient to get this treatment. What does it involve? What was the process like?

STEIN: Yeah, so parts of it were really pretty hard. She had to go through chemo, first of all, to wipe out her own bone marrow to make room for these CRISPR-edited cells. And then Dr. Frangoul infused more than 2 billion of those gene-edited cells into her body, and this was just a few weeks ago.

GRAY: They had the cells in a big syringe, and when it went in, my heart rate shot up real high. And so that was a little scary, tough moment for me. And just after that, I cried, but it was happy tears.

STEIN: What was that feeling like?

GRAY: It was amazing. You know, it was kind of overwhelming after all that I had went through to finally, you know, get what I came for.

STEIN: And Victoria - she calls her new gene-edited cells - she calls them her supercells.

Why do you call them supercells?

GRAY: Well, I have sickle cell, so just replacing it with a better S (laughter) makes it supercells.

SHAPIRO: Rob, it sounds like there's a lot of potential here. But what are the concerns?

STEIN: Yeah, so, you know, there are always concerns about any new, experimental treatment. Is it safe? Will it work? And this is all really magnified with something that's this new. Here's Laurie Zoloth. She's a bioethicist at the University of Chicago. And I talked to her about that.

LAURIE ZOLOTH: I am optimistic about the success of CRISPR. I just want it to be done carefully.

STEIN: Yeah, so they're going to monitor her very closely, first of all to make sure the edited cells are safe, they're not causing any health problems on their own, and then to try to get any clues to see if they might be working. And researchers are planning to study dozens of patients at medical centers in this country and in Canada, in Europe. It could take months, and maybe even years, to know how well it's working.

And I talked to Victoria about that. She says she knows the risks and that it is a very early study, but she can't help but hope that it helps her.

GRAY: I feel like the way everything had been, it was kind of fate. And I feel special to be the first to do it.

STEIN: And we're going to be checking back with Victoria just to see how things are going.

SHAPIRO: That's NPR's Rob Stein with that exclusive story about CRISPR gene-editing technology.